Memory system and method for strobing data, command and address signals

Abstract

A memory system couples command, address or write data signals from a memory controller to a memory device and read data signals from the memory device to the memory controller. A respective strobe generator circuit in each of the memory controller and the memory device each generates an in-phase strobe signal and a quadrature strobe signal. Command, address or write data signals stored in respective output latches in the memory controller are clocked by the in-phase signals from the internal strobe generator circuit. These command, address or write data signals are latched into input latches in the memory device by the quadrature strobe signal coupled from the memory controller to the memory device. In substantially the same manner, read data signals are coupled from the memory device to the memory controller using the in-phase and quadrature strobe signals generated by the internal strobe generator circuit.

1. A method of coupling a command, address or data signal between a memory controller and a memory device, the method comprising:
 generating a first strobe signal in one of the memory controller or memory device; 
 generating a second strobe signal in the memory controller or memory device where the first strobe signal is generated, the second strobe signal having signal transitions that are offset from signal transitions of the first strobe signal by 90 degrees; 
 coupling a command, address or data bit from the memory controller or memory device where the first strobe signal and second strobe signal are generated responsive to a transition of the first strobe signal; 
 coupling the second strobe signal to the other of the memory controller or memory device; and 
 capturing the command, address or data bit at the other of the memory controller or memory device responsive to a transition of the second strobe signal coupled to the other of the memory controller or memory device. 
 
   
   
     2. The method of  claim 1  wherein the first strobe signal and the second strobe signal are generated in the memory controller, and wherein the command, address or data bit is coupled from the memory controller to the memory device and captured in the memory device. 
   
   
     3. The method of  claim 2  wherein the command, address or data bit coupled from the memory controller to the memory device comprises a memory command bit. 
   
   
     4. The method of  claim 2  wherein the command, address or data bit coupled from the memory controller to the memory device comprises a memory address bit. 
   
   
     5. The method of  claim 2  wherein the command, address or data bit coupled from the memory controller to the memory device comprises a write data bit. 
   
   
     6. The method of  claim 5 , further comprising:
 generating a third strobe signal in the memory device; 
 generating a fourth strobe signal in the memory device, the fourth strobe signal having signal transitions that are offset from signal transitions of the third strobe signal by 90 degrees; 
 coupling a read data bit from the memory device to the memory controller responsive to a transition of the third strobe signal; 
 coupling the fourth strobe signal to the memory controller; and 
 capturing the read data bit at the memory controller responsive to a transition of the fourth strobe signal coupled to the memory controller. 
 
   
   
     7. The method of  claim 1  wherein the first strobe signal and the second strobe signal are generated in the memory device, and wherein the command, address or data bit coupled from the memory controller or memory device comprises a read data bit coupled from the memory device to the memory controller and captured in the memory controller. 
   
   
     8. The method of  claim 1  wherein the act of generating a first strobe signal comprises generating a plurality of phases of the first strobe signal that differ from each other by N* 180 degrees, and the act of generating a second strobe signal comprises generating a plurality of phases of the second strobe signal that differ from each other by N* 180 degrees, where N is a positive integer. 
   
   
     9. The method of  claim 8  wherein the act of coupling a command, address or data bit from the memory controller or memory device responsive to a transition of the first strobe signal comprises coupling a bit of the memory command, address or data from the memory controller or memory device responsive to each transition of one of the phases of the first strobe signal, and wherein the act of capturing the command, address or data bit at the other of the memory controller or memory device comprises storing a bit of the memory command, address or data coupled to the other of the memory controller or memory device responsive to each transition of one of the phases of the second strobe signal coupled to the other of the memory controller or memory device. 
   
   
     10. The method of  claim 9  wherein the number of bits of the memory command, address or data coupled from the memory controller or memory device responsive to each transition of one of the phases of the first strobe signal and the number of bits of the memory command, address or data stored in the other of the memory controller or memory device responsive to each transition of one of the phases of the second strobe signal comprise four bits. 
   
   
     11. The method of  claim 8  wherein the act of generating a plurality of phases of the first strobe signal comprises generating strobe signals having phases of 0 and 180 degrees, respectively, and the act of generating a plurality of phases of the second strobe signal comprises generating strobe signals having phases of 90 and 270 degrees, respectively.